The invention pertains to a core breaker for use with an earth strata cutting assembly such as, for example, a continuous mining machine. More specifically, the invention pertains to a core breaker for use with such an earth strata cutting assembly wherein the core breaker contains easily replaceable rotatable cutting tools.
As mentioned above, one example of an earth strata cutting assembly is a continuous mining machine. A typical continuous mining machine typically includes a plurality of rotatable cutting drums that are advanced so as to engage the earth strata (e.g., coal in a vein) and cut or rip the same into fragments. U.S. Pat. No. 3,712,679 to Amoroso shows a continuous mining machine. The earth strata (e.g., coal) that is cut or ripped from the vein falls onto the floor of the mine, and is then handled in a suitable fashion so that it is removed from the vicinity of the continuous mining machine. In a typical continuous mining machine, the cutting drums are spaced apart so that they do not cut across the entire face of the vein. Thus, after completion of the cutting by the cutting drums, there remains a volume of earth strata (or coal) that needs to be removed in order for the continuous mining machine to continue to advance in the cutting operation. In order to remove the remaining earth strata, a core breaker is positioned between each one of the adjacent cutting drums whereby the core breaker includes a plurality of bits that impinge upon the remaining volume of coal so as to break it into fragments.
In a commercial underground mining environment, the core breaker associated with a typical continuous mining machine has a plurality of cutting members secured (such as by welding) to the support of the core breaker. When a cutting member becomes worn (or otherwise is in a non-useful condition), it is not unusual that the core breaker must be removed from the mining machine and then the cutting member is removed such as by cutting with a welding torch. A new cutting member is then welded to the core breaker support and the core breaker is placed back in the mining machine. There also may be situations where the worn cutting member can be cut by a welding torch without removing the core breaker from the mining machine. As can be appreciated, it is not an easy task to remove the core breaker from the mining machine and then install the core breaker in the mining machine. For either situation, it is not an easy task to remove the worn (or non-useful) cutting member by cutting with a welding torch and then re-welding a new cutting member to the core breaker support.
U.S. Pat. No. 4,669,786 to Morgan et al. discloses a core breaker that has replaceable bits (17) held in a support (13). The bit (17) shown in the Morgan et al. patent has an axial forward end that is flat (or blunt). The bit has a blunt axial forward end. A frusto-conical portion extends rearwardly from the blunt axial forward end. A cylindrical portion extends rearwardly from the frusto-conical portion. The cylindrical portion terminates at the axial rearward end of the bit. The bits of the Morgan et al. patent appear to be made out of only one material.
The fact that the tip is blunt would appear to increase the energy (or power) necessary to drive the core breaker of the Morgan et al. patent through the earth strata. In addition to requiring more energy to drive the bit, a bit that has a blunt tip increases the resistance, and hence, increases the forces exerted on the bit. Such an increase in the forces exerted on the bit increases the chance that the bit will fail through breakage. In light of the geometry of the bit and the manner it is held in the support as disclosed in the Morgan et al. patent, it would appear likely that any breakage could be expected to occur at the point where the cylindrical section protrudes out of the support (13). If a bit broke off at this location, it would appear to be very difficult, if not impossible, to remove such a bit from the support.
Even if the bit did not fail by breakage, but merely wore out, it still appears that it would be difficult to replace the bit of the Morgan et al. patent. In this regard, the bit shown in the Morgan et al. patent is retained by the use of a core breaker support that contains what appears to be two bores of different diameters wherein there is a shoulder at the joinder of these bores. A snap ring carried in a groove in the bit abuts against the shoulder. There does not appear to be any way to easily disengage the snap ring, and thus, one would have to pull the bit out of the support against the resistance provided by the abutment between the shoulder and the snap ring whereby the force exerted on the bit would have to be enough to deform the snap ring.
The bit in the Morgan et al. patent appears to be non-rotatable. In operation, the Morgan et al. bits generally flex in one direction opposite the direction of travel of the mining machine. This is especially true of the core breaker bits having a vertical (or a vertical component in its) orientation. The flexure causes the forward side of the bit to experience tension forces and on the rearward side of the bit experiences compressive forces. The continual application of tension and compressive forces on the bit may ultimately result in an early failure of the bit by fatigue.
It further appears that the core breaker support (13) as disclosed in the Morgan et al. patent does not provide for any structural support for the most rearward part of the cylindrical portion of the bit during the operation of the continuous mining machine.
It would thus be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker uses a cutting tool that has a hard carbide tip brazed to the cutting tool at the axial forward end thereof.
It would thus be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker uses a cutting tool that has a relatively sharp hard carbide tip at the axial forward end thereof so as to not increase the energy necessary to drive the core breaker through the earth strata.
It would thus be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker uses a cutting tool that has a relatively sharp hard carbide tip at the axial forward end thereof so as to not increase the resistance to the passage of the cutting tool through the earth strata which therefore does not increase the forces exerted on the cutting tool.
It would thus be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker uses a cutting tool that is relatively easy to extract even after failure.
It would thus be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker provides easily replaceable cutting tools after the tool has become worn to a point where it does not cut in a satisfactory manner.
It would thus be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker uses a cutting tool that is rotatable about its central longitudinal axis so that tension and compressive forces are distributed forces about the circumference of the cutting tool body improving the fatigue life of the cutting tool and preventing the concentration of forces (either tension forces or compressive forces) at one side.
It would also be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker provides structural support for the rearward portion of the cutting tool during the operation of the continuous mining machine.
It would thus be desirable to provide an improved core breaker for use in an earth strata cutting assembly (e.g., a continuous mining machine) wherein the core breaker provides support for the cutting tool so as to prevent it from being driven into the bore.